This invention relates to optically pumped lasers and particularly NdYAG lasers for industrial applications providing high average power in pulsed operation.
An average power of laser radiation of 1 kilowatt or more is desired for various industrial applications including welding or cutting of metals. Gas discharge lasers, particularly using CO.sub.2 as the lasing gas, have dominated these high average power applications. CO.sub.2 lasers operate with a relatively high energy conversion efficiency of about 10% or more and, besides energy, have only the lasing gases as a normal operating consumable. Nevertheless, CO.sub.2 lasers suffer the disadvantages of requiring large mechanical structures and producing radiation at 10.6 micron wavelength which is substantially reflected by most metals. As a consequence of this high reflectance, CO.sub.2 lasers are unsuitable for cutting relatively thick sections of such metals as copper, aluminum, titanium and certain steels. In contrast to CO.sub.2 lasers, optically pumped NdYAG lasers produce laser radiation at 1.06 micron wavelength which is absorbed by metals nearly an order of magnitude more than the radiation of the CO.sub.2 laser. However, NdYAG lasers of known types operate at energy conversion efficiencies of about 2-3% and the pumping flash lamps have a predictable life determined by the energy applied. The flash lamps must therefore be considered as consumables when determining operating costs.
Further, the replacement of flash lamps in known lasers typically requires some disassembly of the laser head.
NdYAG lasers operating in pulsed mode may produce high peak powers desirable for processing metals while maintaining average power at substantially lower levels. However, known NdYAG lasers have not produced sufficient peak power at sufficient pulse repetition rates to cut thinner sections of metals as are used in aircraft at high enough speed to prevent discoloration associated with oxidation and stress of the material surrounding the cut. Therefore neither known CO.sub.2 nor known NdYAG lasers have been accepted by aircraft manufacturers for cutting components for air frames. It is therefore desirable to achieve high average power operation with a NdYAG laser with high pulse repetition rates and at the same time extend the operating life of the laser flash lamps.
While a theoretical limit of average power for a NdYAG laser rod of commonly used dimensions is 900 watts, practical applications limit the operation to a maximum of about 400 watts average power. With typical operating efficiencies of less than 3%, the required power input for 400 watts average power operation is in excess of 16 kilowatts. To achieve a desired power level of near 1 kilowatt, multiple laser amplifiers and a power input in excess of 40 kilowatts would be required. Further, operation of flash lamps at the required high energy levels results in reduced operating life of the flash lamps, effectively increasing the overall operating costs.
In light of the limitations of known high power lasers for industrial application, it is an object of this invention to provide an optically pumped NdYAG laser for high average power operation, operating with substantially improved efficiency.
It is a further object of this invention to provide an optically pumped NdYAG laser for high average power operation providing increased flash lamp life over prior art devices for the same operating conditions.
It is a still further object of the present invention to provide an optically pumped NdYAG laser system providing average power in pulsed operation of at least 800 watts.
It is a still further object of the present invention to provide an optically pumped NdYAG laser system for high average power applications having operating costs which compare favorably with operating costs for CO.sub.2 lasers for the same applications.
It is a still further object of the present invention to provide an optically pumped laser system for high average power applications including cutting relatively thick sections of metals.
It is a still further object of the present invention to provide an optically pumped laser system for high average power applications including cutting of thin sections of metals without discoloration at the periphery of the cut.
Further objects and advantages of the present invention shall become apparent from the attached drawings and descriptions thereof.